Control of polymerization reactions



Feb. 19, 1963 D. E. BERGER ETAL 3,078,265

CONTROL oF POLYMERIZATION REACTIoNs Filed sept. 12. 1957 y 8 sheets-sheet 2 FLOW TRANSDUCER AF2 lob APS Il fo/ mok )L I 14m/0f A iKwI ,f f /o/- FLOW '5 wmf* TRANSDUCER FLOWMETER INVENTORS RDGEABTSN F/G. 2 BY H 4i/M+ Feb. 19, 1963 D. E. BERGER ET AL CONTROL oF POLYMERIZATION REACTIONS 8 Sheets-Sheet 5 Filed Sept. 12. 195'? N S m n u O ES N h. T. GN on m m m .no BT [wd T @E MEA. A .G Y nZw EDR. WM: ov H n w lVwwmmrtE/ .0.o

Feb. 19, 1963 D. E. BERGER ET AL v 3,078,265

CONTROL OF POLYMERIZATION REACTIONS Filed Sept. 12, 195'? 8 Sheets-Sheet 4 AOOIX sERvo y sERvo 1 AMPLIFIER |7| MOTOR D.E.BERGER RG, ATKINSON BY ff g www@ A T TORNEVS Feb. 19, 1963 D. E. BERGER ETAL CONTROL OF' POLYMERIZATION REACTIONS Filed sept. 12. 1957y 8 Sheets-Sheet 5 IIIA AMPLIFIER INVENTOKS DE. BERGER R.G. ATKINSON AMPLIFIER l I (21o AMPLIFIER 207 20s Il/ :20| o6 I A T TORNEI/5 Feb. 19, 1963 D. E. BERGER ET AL CONTROL oF POLYMERIZATION REACTIONS 8 Sheets-Sheet 6- Fled Sept. l2. 195'? AT TORNEI/5 Feb. 19, 1963 D. E. BERGER ET AL CONTROL OF POLYMERIZATION REACTIONS Filed sept. 12. 1957 8 Sheets-Sheet 7 AAAAA INVENTORS D. E. BERGER R.G.ATKINSON ATTORNEYS Feb. 19, 1963 D. E. BERGER ETA;

CONTROL OF POLYMERIZATION REACTIONS mmv Filed Sept. 12. 195'? INVENTORS D E BERGER R.G.ATKINSON A 7' TORNEVS United States Patent O .5,078265H`. v, L CONTROL OF PELYMEEIZATHON REACTEONS, Donald E. Berger and Robertk G. Atkinsomllartlesville,

Okla., assigners to Phillips Petroleum Company, a corpor'atioriof' Delaware Filed'Sept. 12', 1957, Ser. No; 683,662 l''Claims. (Cl. 26d- 949) 'I'his invention relates to the control'y of polymerization' reactions.

Various methods are known for producing normally solid and semisolid polymers. For example, hydrocarbons, such as ethylene propylene, isobutene, butadiene4v and styrene can be plyrnerized, either independently or invar'ious admixtures with one another, to produce solid;

or semisolid polymers. Recently, considerable attention has beenV directed toward the produetin of solid olen polymer, such as polymers' of ethylene and/or propylene. The polymerizations are' frequently carried out in the presence of a4 solid catalyst, utilizing' a liquid solvent as the reaction medium'. The polymerization reactions are exothermi'c so that it becomes necessary to provider is provided for controlling polymerization reactors in' an" automatic manner. The control is based upon a measurement of the heat liberated 'by the polymerization' reaction. This measurement is accomplished by subtracting the heat' supplied to the reactor from the heat' re moved from the reactor. Measurements are made of the flow rates andtemperatures of all the principal streams entering and leaving the reactor. Other sources of heat addition and heat losses are also measured to provide the' total amounts of heatentering and leaving the reactor. In response to the measured heat of reaction, the reactor is controlled in an automatic manner. This can conveniently be accomplished b`y controlling the flo-w of catalyst or monomer into the polymerization reactor.

Accordingly, it is an object of thisA invention to provide an improved method of controlling polymerization reactions.

Another object isto provide apparatusl for controlling polymerization reactions.

A further object is to provide improved polymerization procedures whereby a polymer having uniform properties is produced. v

Other objects, advantages and features of the invention should become apparent from the following detailed description whichV is taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a schematic drawing of a polymerization reactor having the control system of the present invention incorporated vtherein.

FIGURES 2 to 9 are -schematic circuit drawings of elements of the `computer employed in the control system of FIGURE 1.

The present invention is broadly applicable Ato polymerization processes in general, and more particularly to processes in which an oleiin isr contacted with a catalyst in suspension in a solvent. The invention isl especially applicable for use in the production of polymers as described in the copending application of Hogan and Banks, Serial No. 476,306, nled December 20, 1954. As set 2, lforth in thisr copending application in greaterl detail, unique'polymers and' copolymers cani bey produced'by contacting one or more olefins with a catalyst compris-v ing, as an essential ingredient, chromium oxide, preferably including a substantial amount ofliexavalentchrol mium. The chromium oxide is ordinarily associated with at least one other oxide, partieularly at least" onev oxide selected from the group consisting of silica, alu'-n mina, zirconia and thoria. The amountv of chromium,= as chromium oxide, in the' catalyst can range from 0.1 to'l0 or'more weight' percent; Although chromium contents as high as 50weight percent are operative, amounts above 10 weight percent appear to have little addedA ad-' vantage for the polymerization of ethylene. However; for the polymerization of propylene and higher boiling oleiins, chromium contents as'high" as 25 or 30' percent are often advantageous. Onel satisfactory method for producing the catalyst involves the use of a steam-agedV commercial cracking catalyst comprising a` coprecipitatedf gel containing approximately weight' percent silica2 and 1'0 weight' percent alumina. Such' a gel is impregnatedv with an aqueous solution of a chromium com pound ignitable to chromium oxide. Examples c l such compounds are chromium trioxide, chromium nitrate; chromium acetate andammonium chromate. The com- -p'osite resulting from the impregnation' step is d'r'ied and'V then contacted for a period' of several' hours at a temperature of from' about 4:50 to l500 F., preferably'from4 about 900' to 1000 F., for example, with a'- s'tieam of 'ai substantially anhydrous oxygen-containing gas, suchas air.

The ln fe'lforthe polymerization comprises-at least one olefin selected fromtheclass of l-olens having a rn'axnnum of 8 carbon atomsper molecule andno branching nearer` the double bond thanthe 4-posi'tion. ExamplesY of such oleiinsA include ethylene, propylene,' l butene, 1-pentenea'ndf1,3-butadiene.Y C o'polymers, such as ethyleue-propylene copolymers andethylene-'buta'd--' ene copolymers, can be prepared by,the described meth' od. The Apolymerization can 4be effected .at a tempera- Iture in the range 15.0 to.450 F. The pressure can range' from approximately atmospheric to as high asI 1000 p'.s;i`.

A satisfactory method of conducting the polymerization asl disclosed in the above mentioned patent application comprises contacting an olefin .withA a slurry of catalyst in; a hydrocarbon solvent which can existas a'liq'- uid at the temperature of polymerization. In such; a procedure, the reaction pressure needonly be suicient to maintain the solvent substantiallyl in thev liquid phase, and ordinarily ranges from about to` 700"p`.'s.'i. The control -system of the present invention is'particulaly' applicable to this type'` of operation, i.e., one` in which an. o leii'n4 is contacted with a ,catalyst slurry. When utiliz# ing the control method of this invention with this type of process, it has been found4 to be desirable to operate at a temperature such that the polymer is substantially all inl solution in the hydrocarbon solvent. ,This

perature will vary according to the particular solvent which is utilized, e.g'., with paralnsbe'tween about 25.0, and 450 and with` naph'thenes between about 23.0 andusm F. However, if is to' be' understood that file method can be used with processes carried out' at temperatures ysuch that the polymer produced is" in undisysolved solid form.

Suitable solvents for use in the above described proc'- ess are hydrocarbons which are liquid and chemically inert under the reaction conditions. Solvents which ca n be employed advantageously include p arains, such as those having from 3 to l2, preferablyfromj to 9,- car lion atoms per molecule, for example, 2,2,4-trirnethyli pentane (isooctane), normal hexane, normaldecane, iso- Pateatea Feb. 19, tasa pentane, and the like. Another class of solvents which can be employed are naphthenic hydrocarbons having from to 6 carbon atoms in a naphthenic ring and which can be maintained in the liquid phase under the polymerization conditions. Examples of such naphthenic hydrocarbons include cyclohexane, cyclopentane, methylcyclopentane, methylcyclohexane, ethylcyclohexane, the methyl ethyl cyclopentanes, the methyl propyl cyclohexanes, and the ethyl propyl cyclohexanes. The described class of naphthenic hydrocarbons includes condensed ring compounds such as decalin and the alkyl derivatives thereof. A preferred subclass of naphthenic hydrocarbons within the above dened general class comprises those naphthenic hydrocarbons having from 5 to 6 carbon atoms in a single ring and from 0 to 2 methyl groups as the only substituents on the ring. Thus, the preferred naphthenic hydrocarbon solvents are cyclopentane, cyclohexane, methylcyclopentane, methylcyclohexane, the dimethylcyclopentanes, and the dimethylcyclohexanes.

Referring now to FIGURE l of the drawing, there is shown a flow diagram which illustrates diagrammatically a preferred embodiment of the present invention. While the invention is described in conjunction with a particular polymerization process, it is to be understood that it is not intended to so limit the invention. The invention is applicable to any polymerization process in which the material to be polymerized and catalyst are continuously supplied to a polymerization reaction zone.

As shown in FIGURE 1, a suitable solvent, such as cyclohexane, enters a polymerization reactor 30 through an inlet conduit 31 at a temperature of 234 F. This solvent enters the system at a rate of 237,000 pounds per day and has a composition in weight percent as follows:

A feed material, such as ethylene, enters reactor 30 through an inlet conduit 32 at a temperature of 260 F. This feed enters the system at a rate of 34,113 pounds per day and has a composition as follows:

Methane 0.38 Ethane 2.80 Ethylene 95.32 Cyclohexane 1.50

A catalyst enters reactor 30 through an inlet conduit 33. In the particular reaction referred to by way of example, the catalyst is added to the system in the form of a slurry in the solvent, 96% cyclohexane and 4% catalyst. This catalyst is a chromium oxide-silicaalumina catalyst prepared by impregnating a 90 weight percent silica and weight percent aluminum gel composite with chromium trioxide which is dried and heated in air to form a composition containing approximately 2.5 weight percent chromium in the form of chromium oxide, of which approximately one-half is in the form of hexavalent chromium. The catalyst is added at a rate of 2,725 pounds of slurry per day.

Reactor 30 is surrounded by a jacket 34 through which a coolant is circulated. A coil of heat exchange tubes 35 is disposed within the interior of reactor 30. Cooling coil 35 and jacket 34 thus provide a means for removing heat from reactor 30 during the polymerization. Reactor 30 is provided with a stirrer 36 which is driven by a motor 37. Motor 37 is energized from a source of electrical energy, not shown, which is connected to the motor by means of a cable 38. The reactoreiuent is withdrawn through a product conduit 40. This effluent, comprising a mixture of polymer, solvent, spent catalyst and unreacted ethylene, is subsequently passed to suitable separation means to recover the desired polymer.

The reaction mixture in reactor 30 is maintained at a desired temperature by circulating a coolant through jacket 34 and coils 35. It is desirable to employ the same material, cyclohexane, for the coolant as is employed for the solvent. This eliminates any additional separating problems if leakage should occur between the coolant conduits and the interior of the reactor. The coolant is introduced into the system through an inlet conduit 41 which communicates with jacket 34 and coils 35. The coolant is subsequently removed from the system through a conduit 42 which communicates with a flash tank 43. Vapor is removed from flash tank 43 through a conduit 44 which communicates with the inlet of a condenser 45. The condensed vapors are returned to tank 43 through a conduit 46. The liquid in tank 43 is returned to reactor 30 through conduit 41. In order to simplify the drawing, the various pumps and valves and other controllers necessary to establish and control the ows of materials have been deleted.

From an inspection of FIGURE l, it should be evident that heat is added to and removed from reactor 30 in several ways. In accordance with the present invention, the total heat liberated by the polymerization reaction is computed. This computation is made by subtracting the heat which enters the reactor from the heat which is Withdrawn from the reactor. The amounts of these heats are obtained by summing a series of equations which represent the heat transferred into and out of reactor 30.

The first source of heat removal from reactor 30 results from the solvent supplied by conduit 31. This heat Q1 can be calculated from the following equation:

where:

The heat Q2 removed from the reactor by the coolant is represented as follows:

cFKa/Tztcnu. 2)

where:

K2=an orifice constant AP2=pressure differential across an orifice in conduit 41 ATc=temperature difference, defined hereinafter, see FIG- URE 2 C3=specic heat of the coolant The sensible heat Q3 removed by cooling of the condensed vapors from flash tank 43 is represented as follows:

Kazan orifice constant TM=temperature of coolant in conduit 46 a2=density temperature coeicient AP3=pressure differential across an orifice in conduit 46 ATM=temperature difference, defined hereinafter, see

FIGURE 2 Heat is also removed from reactor 30 due to conduction through the insulated walls of the reactor. This heat loss Q4 can be represented as follows:

where z K4=a constant V=temperature difference across reactor walls.

The major amount of heat removal results from the heat of vaporization of the coolant. This is represented as follows:

K3=an orifice constant APV- pressure differential across an orifice in conduit 46 C5=heat of vaporization of the coolant at T1 z=heat of vaporization temperature coefficient Tv=temperature of vapor in tank 43 The heat Q6 removed from the' reactor by the olefin stream is represented as follows:

Q6=F10W (C7) ATE (6) where: Flou/:flow of the olefin C7=specific heat of the olelin ATE=temperature difference, deiined hereinafter, see

FIGURE 2.

Heat is generated within the reactor by rotation of stirrer 36. This heat Q8 is represented as follows:

Qa: (KWLOad-KWNO Load) 3,413 (7) where The heat Q7 removed by the catalyst slurry is assumed to be constant. Heat is also supplied to reactor 36 due to the heat of solution of the olefin in the solvent. This is represented as follows:

QgzFlOWXIs where K5=constant relating to heat of solution.

The various quantities indicated in the foregoing equations are measuured by the apparatus illustrated schematically in FIGURE l. The temperatures of the materials owing through conduits 3l, 32, 4l and 46 are measured by temperature sensing elements Ts, TE, Tc and TM, respectively. The temperature within reactor Sil is measV ured by a temperature sensing element TR. The temperatures of the liquid and vapor in tank d3 are measured by respective temperature sensing elements TF .and TV. The heat loss through the reactor walls is measured by a sensing element L. The heat generated by stirrer 36 is measured in terms of the power supplied to motor 37. This power is measured by a wattmeter KW which can be a thermal converter of the type described in Bulletin 77-39-0-2 of Leeds & Northrup Company,l Philadelphia, Pa., for example. The iiow rates through conduits 3l, 41 and 46 are measured in terms of pressure differences across orifices in the respective conduits. These pressure measurements are made by respective detecting elements APl, AF2, and AP3. The outputs of the several detecting elements of FIGURE l are applied to a computer 43. The output signal of computer 48 energizes a controller 49 which regulates either a valve 5@ in conduit 33 or a valve 5l in conduit 32;. The rate of addition of catalyst or olefin to reactor Sil can thus be regulated to maintain the reaction at a uniform rate, as evidenced by a constant heat output, so as to provide a product having uniform properties.

The various temperatures which are measured by the apparatus of FIGURE l can be conveniently obtained by means of thermocouples. These various thermocouples are illustrated schematically in FIGURE 2. Certain of these thermocouples are provided with cold junctions which are indicated by primed reference characters. Twok separate thermocouples are employed to measure the temperature within reactor 30. These thermocouples are. designated as TR and TR1. The terminals of these Various thermocouples are connected in the manner illustrated in Fl'GURE 2 to provide the Various quantities indicated adjacent the respective terminals which` are designated 5a and 5b, Zaand 2b, Scand 3b, `llfaa'and 135,.,1241 and 12b, 9a and 9b, Sa and 8b, and 6a and 6b. The three differential pressure measurements are applied in sequence to a flow transducer 55. The output of transducer 55 is connected' between terminals 4a and 4b, '7a and 7b, and 16a and lub. The heat lossv through the reactor walls is measured by a series of spaced thermocouples'L having first junctions near the inner walls and "second junctions near the outer walls. The outputs of: these thermocouples thus provide signals which are representativeof the heat transferred through the reactor walls. This signal is applied between terminals lila and 11b. The output signal of wattmeter KW is applied between terminals 14a and 14h. The output signal of liowmeter 47,' which' provides a signal directly related to ethyleneilow, is applied through a transducer 56 to terminals 15a and i511. As will become `apparent from thedetailed description which follows, the several output signals from the apparatus of FIGURE 2 are all direct currentvolta'ges. These voltages constitute the inputs to the computer.

In the described example, TE, TS, Tv, TF, TM, TR and TC are approximately 260 F., 234 F., 230 F., 228 Fl., F., 280 F. and 229 F., respectively. KWLwd is 35 kw. and KWN0 Load is 5 kw. Reactor 3l? has avolume of 3300 gallons.

The detecting elements AP1, AF2 and AP3 provide output alternating current signalsr which are representativeof the pressure differences acrossv the respective orifices. Suitable elements for this purpose are described in'Bulletin A707, the Swartwout Company, Cleveland,l Ohio. These signals are converted by flow transducer' 55 into direct voltages which are proportional to the respective flows. With reference to FIGURE 3, the first output terminal of flow detecting element AP3 is connected to the first end terminal of potentiometer 61. The second output terminal of detecting element AP3 is connected to the second end terminal of potentiometer 61 and to ground. The contactor of potentiometer 6l is connected to a terminal 62 which is adapted to be engaged by a switch 63. Switch 63 is actuated by a relay 64. Flow indicating elements AF2 and API are likewise connected across respective potentiometers 65 and 66. The con# tactor of potentiometer 65 is connectedto a terminal 67 which is engaged by switch 63'when relay 64 is energized.` The contacter of potentiometer 66 i's`connected to a terminal 63 which is engaged by a switch 69 when relay 64 is not energized. Switch 6 3 is connected to a terminal 70 which is engaged by a switch 7l when a relay 72 is not energized, Switch 69 is connected to a terminal 73 which is engaged by ya switch '74 when relay '72 is energized. Switches '7l and 'p74 are connected to the lirst input terminal of an alternating current amplilier 75, the second input terminal of which isconnected to ground.4 Potentiometer 65 actually is not required in the specific example described, and can effectively be eliminated by moving its contactor to the uppermost position.

Relays 64 and 72 are energized selectively` by ach-cuit described in detail hereinafter. When both relays 64 and 72 are deenergized, potentiometer 6l is connected to its amplier 75. When relay 64 alone is energized, potentiometer 65 is connected to ampliiier 75. When relay 72 alone is energized, potentiometer 66 is connected -to amplifier 75. A reference voltage is connected to amplfier ,75 when 64 and 72 are energized. The potentiometers 61 and 66 are employed to multiply the pressure difference signals by density correction factors.

The first output terminal of amplifier 75 is connected through a capacitor 76 to the first end terminal of the primary winding of a transformer 77. The second output terminal of amplifier 75 is connected to ground and to the second end terminal of the primary winding of transformer 77. The end terminals of the secondary windings of transformer 77 are connected to the control grids of triodes 78 and 79, respectively. The center-tap of the Secondary winding of transformer 77 is connected to ground. A resistor 81 is connected in parallel with the secondary winding of transformer 77. The anodes of triodes 78 .and '79 are connected to a terminal S2 which is maintained at a positive potential. The cathodes of triodes 78 and 79 are connected to ground through respective resistors S3 and 84. A source of alternating current 35 of the same frequency as the output signals from elements API, APZ and AP3 is applied across the primary winding of a transformer S6. The first end terminal of the secondary winding of transformer 86 is connected through capacitors 87 and 8S to the cathodes of triodes 78 and 79, respectively. The second end terminal of the secondary winding of transformer 86 is connected to ground. The cathode of triode 79 is connected through series connected resistors 90 and 91 to the first input terminal of a direct current amplifier 92. The cathode of triode 73 is connected through series connected resistors 93 and 94 to the second input terminal of amplifier 92. A capacitor 95 is connected between ground and the junction between resistors 90 and 91 and a capacitor 96 is connected between ground and the junction between resistors 93 and 94.

Triodes 78 and 79 and the circuit elements associated therewith thus form a phase sensitive detector which provides an output direct voltage of magnitude proportional to the alternating input voltage. The output signals from the cathodes of the two tubes are filtered so that a smooth direct voltage is supplied to the input of amplifier 92. The remainder of the circuit illustrated in FIGURE 3 with the exception of elements 250 to 253 is provided to obtain a signal proportional to the square root of the output signal from amplifier 92.

The first output terminal of amplifier 92 is connected through a resistor 100, a variable resistor 101, a resistor 102 and a capacitor 163 to the control grid of a triode 1535i. The control grid of triode 104 is connected to a negative potential terminal 108 through a resistor 117. Resistor 101 is shunted by a non-linear resistance element 105. The cathode of triode 104 is connected to the cathode of a triode 106. These two eathodes are connected through a resistor 107 to a terminal 103 which is maintained at a negative potential. The anode of triode 104 is connected to a terminal 109 which is maintained at a positive potential. The anode of triode 106 is connected to terminal 109 through a resistor 110 and to the control grid of a triode 111 through a resistor 112. The control grid of triode 111 is connected to ground through a resistor 113, The cathode of triode 111 is connected to the ground through a resistor 114 which is shunted by a capacitor 115. The anode of triode 111 is connected to terminal 109 through a resistor 116. The cathode of triode 111 is also connected to the cathode of a triode 118 through a resistor 119. The anode of triode 11S is connected to terminal 109, and the cathode of triode 118 is connected through a resistor 120 to terminal 108. The cathode of triode 118 is connected through a resistor 121 to output terminals 4a, 7a, and 10a. The cathode of triode 118 is also connected to the junction between resistor 102 and capacitor 103 through a resistor 122 and a second nonlinear resistance element 123.

Triodes 104, 106 and 111 and the circuit elements associated therewith thus provide an operational amplifier wherein the output signal is a function of the square root ofthe input signal. This is accomplished by means of the non-linear resistance elements in the input circuit and in the feedback circuit. These elements are selected so that the current flows therethrough are an inverse exponential function of the voltages applied across the elements.

A stabilizing amplifier is provided in the circuit of FGURE 3 to avoid drift in the direct current operational amplifier. The junction between resistor 1.02 and capacitor 103 is connected through a resistor 12S to the first contact 126 of a vibrator assembly. The second contact 127 is connected to ground. A switch 128 vibrates bctween contacts 126 and 127 when a coil 129 is energized by a source of alternating current 130. Contact 126 is connected through a capacitor 131 to the control grid of a triode 132. Switch 128 is connected through a capacitor 133 and a resistor 134 to the anode of a triode 135. The anodes of triodes 132 and 135 are connected through respective resistors 136 and 137 to a terminal 133 which is maintained at a positive potential. The cathodes of triodes 132 and 135 are connected to ground through respective resistors 140 and 141. The control grids of triodes 132 and 135 are connected to ground through respective resistors 142 and 143. The anode of triode 132 is connected through a capacitor 141i to the control grid of triode 135. A capacitor 145 is connected between the anode of triode 132 and ground. Switch 128 is also connected through a resistor 146 to the control grid of triode 106. The control grid of triode 105 is connected to ground through a capacitor 147. The anode of triode 111 is connected to the control grid of triode 110 through a capacitor 150 which is shunted by a resistor 151 and cleo trical discharge tubes 152 and 153 which are connected in series relationship. The control grid of triode 113 is connected to ground through a resistor 154.

The alternating current amplifier thus formed by triodes 132 and 135 forms a feedback network in the direct current amplifier in order to stabilize the direct current amplifier against drift.

The direct voltages which appear between the several pairs of terminals of FIGURE 2 are converted into correspending potentiometer settings in order to perform the multiplications required to solve the heat transfer equations. These voltages are converted into the respective potentiometer settings in sequence and repetitively by means of a stepping switch. The circuit employed to establish the potentiometer settings is illustrated schematically in FGURES 4 and 5. The output terminals of FIGURE 2 are represented in FIGURE 4 as the a and b terminals of the stepping switch. The a terminals are engaged in sequence by switch arm A and the b terminals are engaged in sequence by switch arm B. The switch arms move between adjacent terminals each time a solenoid 150 is energized. The stepping switch preferably is of the rotary type so that the switch arms move successively to adjacent contacts and then repeat the operation. The stepping switch employed in one particular embodiment of this invention had 25 contacts associated with each switch arm. The computing operation of the described example can be accomplished with less contacts, although some of the additional contacts are employed in the calibration steps described hereinafter.

Switch arm A is connected to a terminal 151 which is engaged by a switch 152 when a relay 153 is deenergized. Switch arm A is also connected to a terminal 154 which is engaged by a switch 155 when a relay 155 is deenergized. Switch 155 is connected through a resistor 157 to switch arm D of the stepping switch. Switch arm B is connected to a terminal 153 which is engaged by switch 159 when relay 153 is deenergized. A resistor 404 and a capacitor 405 are connected in parallel between switch arm B and ground. Switch arm B is also connected to a terminal 161 which is engaged by a switch 162 when relay 156 is deenergized. Switch 162 is connected to a terminal 164 which is engaged by switch 165 when a relay 166 is deencrgized. Switch 165 is connected to the first input terminal of servo amplifier 165,2. The second input terminal of amplifier 163 is connected to switch arm C of the stepping switch. A capacitor 169 is connected between terminal 164 and switch arm D. The first output terminal of amplifier 9 163 is connected to a terminal 17d and to a switch 171 which engages a terminal 172 when a relay 173 is energized. Terminal 172 is connected to the first input terminal of a servo motor 174. The second output terminal of amplifier 168 and the second input terminal of motor 174 are grounded.

Terminals 1c and 2c of the stepping switch are connected to a terminal 176; terminals 1e and 2e are connected to a terminal 177; terminals 1f and 2f are connected to a terminal 178; and terminals 1d and 2d are connected to a terminal 179. A variable resistor 121i, a resistor 181, and a battery 182 are connected in series relatio-nship between switch arms E and F. A resistor 183 and a standard cell 184 are connected in series relationship between switch arm E and a terminal 1:35 which is engaged by switch 165 when relay 16e is energized. Terminals 176, 177, 178 and 179 are connected to the circuit illustrated in FIGURE 5. Terminal 176 is ccnnected to the junction between resistors 180 and 131. The second terminal of resistor 18d is connected to terminal 178, and the second terminal of resistor 131 is connected to terminal 177. A resistor 183', a potentiometer 184', and a resistor 135' are connected in series relationship between terminals 173- and 177. Resistors 186 and 187 are connected in parallel with the potentiometer 184. Terminal 179 is connected by means of a conductor 188 which forms a temperature compensating thermocouple cold junction, to the contactor of potentiometer 184.

Terminal 170 of FIGURE 5 is connected to a switch 19t) which engages a terminal 191 when a relay 192 is energized. Terminal 191 is connected through the first coil 193 of a reversible two-phase induction motor 194 to ground. One terminal of the second coil 195 of motor 194 is connected to a terminal 196. The second terminal of coil 195 is connected to a terminal 197 which is engaged by a switch 19S when relay 192 is energized. Switch 19S is connected to a terminal 199. An alternating current source described hereinafter is connected between terminals 196 and 199. The drive shaft of motor 194 is connected to the contactor of potentiometer 184. The drive shaft of motor 194 is also connected to the contactors of potentiometers 201 and 202.

The circuit of FIGURES 4- and 5 forms a self-balancing potentiometer. The input signal appears between the first input terminal of amplifier 168 and switch arm D. This signal is balanced against a reference voltage in the bridge network so that any potential difference ener-gizes motor 194 through amplifier 168. This portion of the circuit of FIGURES 4 and 5 comprises a conventional balancing circuit of the general type described in Bulletin No. B-43, Minneapolis-Honeywell Regulator Co., Brown Instrument Division, Philadelphia, Pa. If the input signal differs from the reference voltage motor 194 is energized to adjust the position of the contactor of potentiometer 184. This adjustment continues until the circuit is restored to a set of balance. The rotation of motor 194 required to establish this balance is, therefore, a function of the magnitude of the input signal. This rotation also establishes the positions of the contactors of potentiometers 2131 and 292.

The computer of this invention is also provided with thirteen additional networks, not shown, of the general form of FIGURE 5. The first of these additional networks is connected into the circuit of FIGURE 4 by means of terminals 176', 177, 178 and 179'. The last of these additional networks is connected into the circuit of FIGURE 4 by means of terminals 17671, 177:1, 17n, and 17911. The potentiometers of these fourteen networks are adjusted sequentially as the arms of the stepping switch move to adjacent contacts. This entire stepping operation is repeated periodically to reset the potentiometers representative of changes in the variables to be measured.

One of the networks employed to perform the multi- 10 Y plication required to solve the heat transfer equations indicated above is illustrated in FIGURE 7. A source of alternating current 20S is connected across a potentiometer 206. The primary winding of a transformer 207 is connected between the contactor and one end terminal of potentiometer 296. The secondary winding of transformer 207 is connected across a potentiometer 261:1. A potentiometer 208, having a grounded center tap, is connected across the secondary winding of transformer 297. The contactor of potentiometer 29151 is connected to the first input terminal of an isolation amplifier 209. The first output terminal of amplifier 2119 is connected to the first end terminal of a potentiometer 2Mb. The second end terminal of potentiometer 291i: is connected to ground. The contactor of potentiometer 291b is connected to the first input terminal of an isolation amplifier 210. The first output terminal of amplifier 211) is connected to the rst end terminal of potentiometer 201e. The second end terminal of potentiometer 261e is connected to ground. The contactor of potentiometer 291C is connected to the first input terminal of an amplifier 211. The first output terminal of amplifier 211 is connected to an output terminal 212:1. The second output and input terminals of amplifiers 2139, 216 and 211 are connected to ground.

With reference to Equation 1, it can be seen that there are three principal quantities to be multiplied to obtain the product. These three variables are represented by the three potentiometers 29M, 2Mb and 291C of FIG- URE 7. The indicated multiplication is provided by these three cascade connected potentiometers. The isolation amplifiers are employed to prevent current from being drawn from the potentiometers. Circuits similar to the circuit of FIGURE 7 are provided for each of the other heat transfer equations to be solved. The equations which have fewer than three variables to be multiplied require fewer potentiometers. These circuits are otherwise similar to the circuits of FIGURE 7.

The output signals of the plurality of multiplying circuits of the form of FIGURE 7 are applied to terminals 212:1, 212b 212i of FIGURE 8. These terminals are connected through respect-ive resistors 213m, 213b 213i to the first input terminal of a summing amplifier 430. The rst output terminal of amplifier 480 is connected through a capacitor 214 to the first input terminal of a recorder-controller 215. The second input terminal of controller 215 is connected to ground. The signal applied to controller 215 represents the amount of heat liberated by the polymerization reaction. 'I'his is obtained from the addition of the heat transfer equations, plus or minus depending upon whether heat is added or subtracted. This signal is applied through a conventional control medium to regulate either valve 5f) or valve 51. If the indicated heat of reaction should increase, the rate of addition of olefin or catalyst to the reactor is decreased. If the indicated heat of reaction should decrease, the fiow of olefin or catalyst is increased. It is thus possible to maintain the reaction at al steady rate which results in the production of polymer of uniform quality. This control operation is described in greater detail hereinafter.

Servo amplifier 168 is illustrated in FIGURE 6. The first input terminal 2219 (connected to switch of FIGURE 4) is connected to a switch 221 which vibrates between contacts 222 and 223 when a coil 224 is energized by a source of alternating current 225. Contacts 222 and 223 are connected to the respective end terminals of the primary winding of a transformer 226. The second input terminal 227 (connected to Switch C of FIGURE 4) of ampli-fier 16S is connected to the center tap of the primary winding of transformer 226. The first end terminal of the secondary winding of transformer 226 is connected to the control grid of a triode 228. The second end terminal of the secondary Winding of transformer 226 is connected to ground. A capacitor 229 is connected in parallel with the secondary winding of transformer 226. The cathode of triode 228 is connected to ground through a resistor 230 which is shunted by a capacitor 231. The anode of triode 228 is connected through resistors 232 and 233 to a terminal 234 which is maintained at a positive potential. A capacitor 235 is connected between ground and the junction between resistors 232 and 233. The anode of triode 228 is also connected through a capacitor 236 to the first end terminal of a potentiometer 237. The second end terminal of potentiometer 237 is connected to ground. The contactor of potentiometer 237 is connected to the control grid of a triode 238. The cathode of triode 238 is connected to ground through a resistor 240. The anode of triode 238 is connected to terminal 234 through a resistor 241. The anode of triode 236 is also connected to ground through a capacitor 242 and resistors 243, 244, 245, 246 and 247 which are connected in series relationship.

The circuit thus far described in FIGURE 6 converts a direct current input signal into an alternating signal which is amplified. The voltage dividing network formed by resistors 243, 244, 245, 246 and 247 permits output signals of different amplitudes to be applied to the individual servo motors. This compensates for input signals of different amplitudes. In one particular computer which has been constructed, the output circuit from the voltage dividing network was of the conguration illustrated in FGURE 6. The output terminals 1g, 2g 16g of the stepping switch are connected to the indicated points on the voltage dividing network.`

Switch arm G is connected to the control grid of a triode 258. The cathode of triode 250 is connected to ground through a resistor 251 which is shunted by a capacitor 252. The anode of triode 250 is connected through a resistor 253 to a terminal 254 which is maintained at a positive potential. The anode of triode 250 is also connected through a capacitor 255 to the control grids of triodes 256 and 257. The cathodes of these triodes are connected to ground through a common resistor 258. The anodes of triodes 256 and 257 are connected to the respective end terminals of the secondary winding of a transformer 260. A source of alternating current 261 is directed across the primary winding of transformer 260. The center tap of the secondary winding of transformer 260 is connected to terminal 170. One terminal of current source 261 is connected to terminal 196, and the second terminal of current source 261 is connected through a capacitor 264 to terminal 199. Terminals 170, 196 and 199 energize servo motor 194 of FIGURE 5. The center tap of the secondary winding of transformer 260 is connected to a switch 265 which engages a terminal 266 when a relay 267 is energized. Terminal 199 is connected to a switch 268 which engages a terminal 269 when relay 267 is energized. Terminal 266 is connected through the first winding 270 of twophase induction motor 174 to ground. Terminal 269 is connected through the second winding 271 of motor 174 to the first terminal of current source 261.

The output signal of the motor drive amplifier of FIG- URE 6 thus energizes one of the servo motors 194 of FIGURE when a relay 192 of FIGURE 5 is energized. The standardization motor 174 is actuated when relay 267 is energized. A single servo amplifier thus energizes a plurality of motors in sequence to perform the balancing operations and standardizing functions.

The stepping switch employed to establish the Variables in sequence is actuated by the circuit illustrated in the lower portion of FIGURE 6. The cathodes of triodes 256 and 257 are connected through a resistor 280 to the control grid of a triode 281. A capacitor 282 is connected between the control grid of triode 281 and ground. The cathode of triode 281 is connected to ground through a resistor 283, and the anode of triode 281 is connected to a positive potential terminal 284 through a resistor 285. The anode of triode 281 is also connected to the first end terminal of a potentiometer 286, the second end terminal of potentiometer 286 being connected to a negative potential terminal 287.

The contactor of potentiometer 286 is connected di rectly to the control grid of a triode 288 and through a resistor 290 to the control grid of a triode 291. The cathodes of triodes 288 and 291 are connected to ground. The anodes of these triodes are connected to terminal 284 through a resistor 292. The anodes of triodes 288 and 291 are also connected through a resistor 293 to the control grid of a triode 294. The control grid of triode 294 is connected through a resistor 295 to negative potential terminal 287. The cathode of triode 294 is connected directly to ground, and the anode of triode 294 is connected through a resistor 296 to positive potential terminal 284. The anode of triode 294 is also connected through a ycapacitor 297 to the control grid of triode 291.

The anode of triode 294 is connected to a terminal 300 which normally is engaged by a switch 301. Switch 38-1 is connected through series connected resistors 302 and 383 to negative potential terminal 287. The junction between these resistors is connected to terminals 1h, 2h 15h. These terminals are engaged by switch arm H of the stepping switch. Switch 301 is also adapted to engage a terminal 304 which is connected to a switch 305. Switch 305 normally engages a terminal 306 which is connected through a resistor 307 to positive potential terminal 284. Switch 305 can also engage a terminal 388 which is connected to ground. Switch arm H is connected through a resistor 310 to the control grid of the triode 311. The cathode of triode 311 is connected to ground, and the anode of triode 311 is connected through a resistor 312 to positive potential terminal 284.` The anode of triode 311 is connected through neon lamps 313, 314 and 315 and a resistor 316 to negative potential terminal 287. The junction between lamp 315 and resistor 316 is connected through a resistor 318 to the control grid of a triode 319 and through a resistor 320 to the control grid of a triode 321. The cathodes of triodes 319 and 321 are connected to ground. The anodes of triodes 319 and 321 are connected to the first terminals of a resistor 322 and solenoid 150. The second terminals of resistor 322 and solenoid are connected to the junction between a rectifier 333 and a capacitor 334. Current source 261 is connected across the primary winding of a transformer 336. The first end terminal of the secondary winding of transformer 336 is connected through a resistor 337 to rectifier 333. The second terminal of the secondary winding of transformer 336 and the second terminal of capacitor 334 are connected to ground. A positive potential thus appears at the junction between rectifier 333 and capacitor 334.

The anodes of triodes 319 and 321 are connected through series connected resistors 340 and 341 to the control grids of triodes 256 and 257. A capacitor 342 is connected in parallel with resistor 341. The junction between resistors 340 and 341 is connected through a resistor 343 to negative potential terminal 287.

Terminal 16h of the stepping switch is connected through a resistor 345 to the grounded cathode of triode 294. Terminals 17h to 25h are connected to a first interrupter contact 346 of the stepping switch. The interrupter switch 347 is connected through a resistor 348 to terminals 17h to 25h. A capacitor 349 is connected in parallel with resistor 348. A resistor 350 is connected between terminals 17h to 25h and negative potential terminal 287.

In order to `describe the switching operation, it is assumed that the input signal from one of the transducers is different from the signal last applied from this partcular transducer. This results in lthe potentiometer circuit being unbalanced so that the servo motor is energized to restore a balanced condition. At this time there is a these triodes.

relatively small direct current through triodes 256 and 257. The cathodes of these two triodes are thus maintained at a relatively small positive potential. This potential is inverted by triode 231 -so that a potential is applied to the control grid of triode 238 which permits this triode to con-duct. Conduction by triode 288 results in the potential applied to the control grid of triode 294 being sutiiciently small to extinguish conduction by triode 294. This effectively applies a positive pulse to the control grid o triode 291 which causes it to conduct. Triodes 283 and 291 thus operate essentially in parallel. The potential at the anode of triode 294 is applied through the stepping switch to the control grid of triode 311. The decreased potential at the anode of triode 311 is in turn applied to the control grids of triodes 319 and 321 to keep these two triodes from conducting.

When the bridge circuit becomes balanced, the direct current through triodes 256 and 257 increases substantially to increase the potential applied to the control grid of triode 231. This results in the potential at the control grid of triode 288 being decreased sufliciently to extinguish conduction by this triode. However, triode 291 continues to conduct until the original charge on capacitor 297 leaks off. This incorporates a delay, which can be of the order of one second, for example. At the end of this period, conduction through triode 291 is eX- tinguished so that the potential at the control grid of triode 294 is increased. The resulting conduction by triode 294 results in the potentials at the control grids of triodes 319 and 321 being increased to cause conduction through This energizes solenoid 150 to cock the stepping switch. The resulting negative pulse at the ano-des of triodes 319 and 321 i's applied to the control grids of triodes 256 and 257. This negative pulse reduces the potential of the two cathodes to restore the condition initially described. This initial condition results in conductio-n through triodes 319 to 321 being eX- tinguished to enable the arm of the stepping switch to move to the next contacts.

The purpose of the delay in the multivibrator formed by triodes 238 and 291 is to delay cocking of the stepping switch for a given time after the null signal level is reached at the cathodes of triodes 256 to 257. This insures that the po-tentiometer circuit reaches a nal balanced condition before the next variable is engaged by the stepping switch. The pulse fed back to the servo amplifiers from triodes 319 and 321 assures release of they stepping switch solenoid once it has been cocked. The interrupter switch 347 moves the stepping switch rapidly from contacts 17h to 25h and back to 1h. At position 16h, the control grid of triode 311 is connected to ground through resistors 3111 and 345.

The several servo motors 194, as shown in FIGURE 5, are energized in sequence by the associated relay 192 being energized. These relays are actuated by triodes 360o, 360b 36611 of FIGURE 9. The cathodes of each of these triodes are connected to ground. The anode of triode 369e, for example, is connecte-d to a terminal 361e which is connected to the rst terminal of relay 192 of FIGURE 5, the second terminal of the relay being connected to a positive potential terminal 377. The anodes of the remaining triodes are likewise connected to a relay which energizes a respective one of the servo motors. The grids of triodes 369e, 36017 3631i are connected to respective terminals 2i, 3i 151' of the stepping switch. The co-ntrol grids of triodes 361m, 360b 36911 are also connected through respective resistors 362:1, 362b 362n to the junction between resistors 364 and 365. A spare triode 360o also is provided. The second terminal of resistor 364 is connected to a negative potential 366, and a second terminal of resistor 365 is connected to ground. A capacitor 367 is connected in parallel with resistor 365.

A terminal 370 is connected to the secondary winding 'of transformer 336 of FIGURE 6. Terminal 376 is v 14 connected through a resistor 371, a rectier 372, and a capacitor 373 to ground. The anode of a triode 374 is connected through relay coil 267 to the junction between rectilier 372 and capacitor 373. The cathode of triode 374 is connected to ground. The control grid of triode 374 is connected to terminal 1i of the stepping switch and to the control grid of a triode 375. The control grid of triode 374 is also connected to the junction between resistors 364 and 365 through a resistor 376. The anode of triode 375 is connected through relay coil 166 to the junction between rectifier 372 and capacitor 373. The cathode of triode 375 is connected to ground. Terminal 377 is connected between rectifier 372 and capacitor 373.

The potentiometer circuit of the computer is standardized when switch arm I engages terminal 1i. At this time triode 374 conducts so as to energize relay 267, see FIGURE 6. This connects the output signal from the amplifier of FIGURE 6 to standardizing motor 174. Motor 174 then adjusts resistor 186 of FIGURE 4 until there is a zero signal applied to the input of amplifier 163. Relay 166 is also energized at this time so that a voltage from standard cell 134 is applied to the input of amplilier 163. This operation standardizes the potentiometer circuit of FIGURE 4.

Each time the arms of the stepping switch move to the next contacts, interruptor switch 347 of FIGURE 6 momentarily engages contact 346. This applies a positive pulse from terminal 336 of FIGURE 6 through a capacitor 331 to the control grid of a triode 332 of FIG- URE 9. The cathode of triode 332 is connected to ground. The control grid of triode 382 is connected to a negative potential terminal 399 through a resistor 383. The anode of triode 332 is connected through a resistor 334 to a positive potential terminal 335. The anode of triode 332 is also connected through a capacitor 336 to the control grid of a triode 337. The cathode of triode 337 is connected to ground. The anode and control grid of triode 337 are connected to terminal 385 through respective resistors 338 and 339. The anode of triode 387 is also connected through a resistor 391 to the control grid of triode 332. The anode of triode 382 is ocnnected through a resistor 392 to switch arm I.

This circuit provides a pulse which maintains the motor relay triodes 369 non-conductive for a predetermined time during and after movement of the switch arms ot the stepping switch. The positive pulse from the interrupter switch 347 causes triode 382 to conduct and thereby extinguish conduction through triode 387. Triode 382 continues to conduct until suicient charge leaks oi capacitor 336 to render triode 382 non-conductive once again. The resulting increased potential at the end of triode 332 is applied through switch arm I to cause the associated triode 3611 to conduct. This delay prevents power from being applied to the servo motors until switching transients in the potentiometer circuits and amplier 163 have died out.

The computing circuit is also provided with apparatus for checking periodically the operation of the transducers and of the computer itself. With reference to FIGURE 4, there is shown a plurality of potentiometers 401151, 401912 4661 which are adapted to provide preset voltages. The iirst terminals of all these potentiometers are connected to a negative potential terminal 401. The second terminals of all these potentiometers are connected to ground. The contactors of these potentiometers are connected to the indicated k terminals of the stepping switch. Switch arm K is connected to a terminal 403. Switch 152 of FIGURE 4 is connected to a terminal 4116 which is connected to the control grid of a triode 407 in FIGURE 9. Switch 159 of FIGURE 4 is connected to a terminal 433 which is connected to the cathode of triode 4117 of FIGURE 9. Terminal 370 of FIGURE 9 is connected through a capacitor 4113, an inductor 411 and a capacitor 412 to ground. The junction between capacienvases tor 410 and inductor 411 is connected through a rectilier 413 and a resistor 414 to terminal 408. The junction between capacitor 412 and inductor 411 is connected through a resistor 415 to terminal 486. The junction between capacitor 412 and inductor 411 is connected through a capacitor 417 to the junction between rectifier 413 and resistor 414. A potentiometer 418, having a grounded contactor, is connected between terminals 486 and 498. The anode of triode 487 is connected through a resistor 429 to terminal 335. The anode of triode 487 is also connected through resistor 421 and a neon lamp 422 to ground. The anode of triode 407 is connected through a resistor 423 to a terminal 424 which is connected to the junction between resistors 382 and 383 of FIGURE 6.

During one portion of the checking cycle, relay 153 is de-energized so that the signals between the a and b contacts of the stepping switch are applied between the control grid and cathode of triode 487, FIGURE 9. This triode normally conducts. However, if an open circuit should occur in the transducing elements, conduction by triode 487 is extinguished which increases the potential at the anode thereof. This increase in potential causes neon lamp 422 to conduct so as to provide a warning signal. The resulting positive pulse is also applied through terminal 424 to the lz contacts of the stepping switch, FIGURE 6, to prevent the stepping switch from moving further.

The circuit which operates relays 153 and 156 of FIG- URE 4 and relays 64 and 72 of FIGURE 3 is illustrated in FIGURE 9. Switch arm J of the stepping switch is connected to a source of positive potential 438. Terminals 1i, 2j, 3j and 4j are connected through a resistor 431 to the control grid of a triode 432. Terminals 5j, 6j and '7j are connected through a resistor 433 to the control grid of a triode 434. The cathodes of trodes 432 and 434 are connected to ground. The anode of triode 432 is connected by a terminal 435 through relay 72 of FIGURE 3 to a positive potential terminal 436. The anode of triode 434 is connected by a terminal 437 through relay 64 of FIGURE 3 to a positive potential terminal 438. The grids of triodes 432 and 434 are connected through respective resistors 440 and 441 to the junction between resistors 364 and 365. The control grids of triodes 432 and 434 are also connected through respective resistors 442 and 443 to the anode of a triode 445. The anode of triode 445 is connected through relay 153 of FIGURE 4 and a resistor 446 to a positive potential terminal 447. The anode of triode 445 is also connected through a capacitor 448 to the control grid of a triode 449. The cathodes of triodes 445 and 449 are connected to ground. The anode of triode 449 is connected through relay 156 and a resistor 450 to terminal 447 and to terminal 19j. Terminal 19j is also connected to a negative potential terminal 451 through resistors 452 and 453. A resistor 454 and a neon lamp 455 are connected in series relationship with one another and in parallel with resistor 450. A resistor 456 is connected between the junction between resistors 452 and 453 and the junction between resistor 450 and relay 156. The anode of triode 449 is also connected through a capacitor 458 to the control grid of triode 445.

Terminal 16j is connected through a resistor `469 to the control grid of triode 449. Terminal 25j is connected to ground through resistors 461 and 462. A capacitor 463 is connected between the control grid of triode 449 and the junction between resistors 461 and 462. The control grid of triode 449 is also connected to a switch 464. Switch 464 is adapted to engage a terminal 465 which is connected to the junction between resistors 364 and 365 or a terminal 466 which is connected to a switch 467. Switch 467 is connected to ground when closed.

Triodes 445 and 449 form a non-stable multivibrator. Each time switch arm I engages terminal 16j current `ows through resistor 460 to charge capacitor 448. Re-

sistor 468 is extremely large so that capacitor 448 charges quite slowly. Capacitor 448 is charged to some extent each time switch arm l moves past terminal 16j. The charge on capacitor 443 thus increases stepwise. Triode 445 of the multivibrator normally conducts. This situation continues until the charge on capacitor 448 increases sutiiciently to cause triode 449 to conduct, which occurs after a relatively large number of cycles of the stepping switch. Conduction by triode 449 extinguishes conduction by triode 445. This energizes relay 156 and deenergizes relay 153. Under this condition, the standard voltages from the potentiometers of FIGURE 4 are connected in the circuit in place of the voltages from the transducers of FIGURE 1. The output signal of the computer at this time should have a predetermined value in view of the standard input signals. Pulses generated at position 25j are coupled through capacitor 463 to the grid of triode 449 to insure that the multivibrator ips at position 25j only and not during normal scanning of the variables (positions 2 through 15).

This overall operation of the computer is checked by means of the circuit shown in FIGURE 8. The second terminals of resistors 213e, 213b 213i are connected to the rst input terminal of a summing amplier 480 which is provided with a feedback resistor 480e. The rst output terminal of amplifier 488 is connected through a resistor 4-31 to the control grid of a pentode 482. The second input and output terminals of amplier 480 are connected to ground. The control grid of pentode 482 is connected to ground through a variable resistor 483. The cathode and suppressor grid of pentode 482 are connected to ground through a resistor 484 which is shunted by a capacitor 485. The anode of pentode 482 is connected through a resistor 486 to a terminal 487 which is maintained at a positive potential. The screen grid of pentode 482 is connected to terminal 487 through a resistor 488 and to ground through a resistor 489 which is shunted by a capacitor 49).

Alternating current source 205 is connected across the primary winding of a transformer 492. The rst end terminal of the secondary winding of transformer 492 is connected to ground through a potentiometer 493. The second end terminal of the secondary winding of transformer 492 is connected to ground. The contactor of potentiometer 493 is connected through a capactor 494 and a resistor 495 to the control grid of pentode 482. The junction between capacitor 494 and resistor 495 is connected to ground through a resistor 496.

The anode of pentode 482 is connected through a capacitor 500 to the rst end terminal of a potentiometer 501. The second end terminal of potentiometer 501 is connected to ground. A capacitor 502 is connected between the anode of pentode 482 and ground. The contactor of potentiometer 581 is connected to the control grid of a triode 583. The anode of triode 503 is connected to terminal 487 through a resistor 504, and the cathode of triode 503 is connected to ground through a resistor 585 which is shunted by a capacitor 586. The anode of triode 503 is connected through a capacitor 507 to the control grid of a triode 588. The control grid of triode 588 is connected to ground through a resistor 509. The cathode of triode 508 is connected to ground through a resistor 510, and the anode of triode 503 is connected to terminal 487 through a resistor 511.

The sum of the voltages from the several multiplying units of FIGURE 7 is thus applied to the control grid of pentode 482. A reference signal which is out 0f phase with this summed signal is also applied to the control grid of pentode 482 from current source 205. The magnitude of the dilerence between the output and reference signals at junction of 481, 495 and 483 can be varied by adjustable resistor 483 to determine the magnitude of the permissible error. If the overall computer network is operating properly with the reference voltages being applied to the input terminals, the output signal envases |17 from pentode #82y is zero. However, `if an error has occurred any place in the computer network, the two voltages being compared are no longer equal so'that an output signal is provided by pentode 482. The amplifier circuit formed by triodes 563 and Sti is biased so that the output signal from triode 50S never exceeds a predetermined value, that is, thel amplifier output is clipped.

The circuit shown in the remainder of FGURE 8 forms a multivibrator which normally provides output pulses at a predetermined frequency during operation of the computer. The cathodes of triodes 513 and 514 are connected to ground. kThe anode of triode 513 is connected to terminal 487 through a resistor SiS, and the anode of triode 514 is connected to terminal 487 through resistors 516 and 517. The control grid of triode 513 is connected to terminal 4S'7 through a resistor 518. A capacitor S19 is connected between the anode of triode 514 and the control grid of triode 513. A capacitor 520 is connected between the anode of triode 513 and the control grid of trio-de 5M. The control grid ot triode 514 is connected to a switch S21 which is adapted to engage terminals S22 and 523. Terminal 523 is connected to ground through a resistor 524. The checking circuit of FIGURE 8 is turned ofi when switch S21 engages terminal 523. Terminal 522 is connected through a resistor 525 to the contactor of potentiometer 526. The iirst end terminal of potentiometer 526 is connected through a resistor 527 to a negative potential terminal S28. The second end terminal of potentiometer 526 is connected through a resistor 529 to a terminal 530 which is connected to the anode of triode 4549 of FiGURE 9.

During normal operation of the computer, the `bias applied to the control grid of triode 514 from potentiometers 526 is such that the multivibrator formed by triodes S13 and 514 provides an output pulse at predetermined intervals, which can be of the order of one-half second, for example. The junction between resistors 5to and 5117 is connected through a capacitor 532 to a terminal 533 which is connected to terminal 16h of FIGURE 6. The resulting pulses move the stepping switch past the 16th contacts. The anode of triode Sii is connected through a capacitor 535 to the positive terminal of a rectifier S36 and to the negative of a rectifier 537. The positive terminal of rectifier 537 is connected to ground. The negative terminal of rectiiier 536 is connected to ground through a resistor S38 which is shunted by a capacitor 539. An output signal from triode Sti thus results in a negative signal appearing at the control grid of triode 514. This signal extinguishes lconduction through triode 514 so that the pulses applied to -terminal 16h of FIG- URE 6 are discontinued. This operates to sto-p :further movement of the stepping switch. The iiow detecting elements 61, 65 and 66 are checked when relays 64 and '72 of FiGURE 3 are both energized. This connects the input of amplier 75 to the contactor `of a potentiometer 256. One end terminal of potentiometer 250' is connected to ground. The second end terminal of potentiometer 250 is connected through a variable resistor 251 and a resistor 252 to the first end terminal of the secondary winding of transformer 86. A capacitor 253 is connected in parallel with resistor 252. A reference check voltage is thus applied from source 35 to the input of amplifier 75.

it should be evident from the foregoing description that many of the terminals shown are merely for the purpose of designating connections between the several iigures. Also, many of the switches are for the purpose of turning oi portions of the apparatus or to permit manual opera tion for test purposes.

The circuit illustrated normally provides an automatic computation of the heat liberated by the polymerization reaction. The sources of heat removal from the reactor are indicated as signals of a first polarity whereas the sources of heat addition are indicated as signals of a second polarity. The sum provided by the circuit of FIG- URE 8 thus represents the net heat of reaction. This inal signal is an alternating voltage. Controller 21S conerts this signal into an output control signal, such as a pneumatic pressure which regulates valve 5t) or valve Si of FIGURE 1. This can be accomplished by a transducer of the type described in Bulletin A-7l0, the Swart- Wout Company, Cleveland, Ohio. ln one speciiic embodiment of the control system, valve 5o can be represented by a variable stroke piston pump to pass the catalyst slurry. The control signal can adjust the stroke or speed of the pump. A conventional control valve can also be employed for this purpose. This invention thus provides an eiiicient procedure for regulating polymerization in response to a measurement of the heat liberated by the reaction. It should be evident that in some polym erization systems, certain of the variables measured in the example normally yare suiciently constant as to be omitted. lThe control system can thus be simplilied in these applications.

While the invention has been described in conjunction with a present preferred embodiment, it should be evident that it is notlimited thereto.

What is claimed is:

l. In a polymerization system wherein the material to be polymerized, a catalyst, and a diluent are directed to a polymerization reactor, the mixture is agitated in said reactor, a coolant is passed in thermal contact with said reactor, and the resulting product is removed from said reactor; a control system comprising, means to measure the temperature and flow rate of the material to be polymerized, -means to measure the temperature and iiow rate of the diluent, means to measure the temperature of the material in the reactor, means to measure the `heat sup- .plied to the reactor by the agitation of the mixture in said reactor, means to measure the heat lost from the reactor to the surrounding atmosphere, means to' measure the flow -rate of coolan-t to said reactor and the temperatures of the coolant supplied to and removed from said reactor, means responsive to said means to measure to compute the ditierence between the heat removed from said reactor and the heat supplied to said reactor, and means responsive to said means to compute to control the polymerization reaction to tend to maintain the reaction at a uniform rate.

2. The control system of claim l wherein sm'd means to control comprises means to reduce the flow of catalyst to said reactor when the heat difference increases above a predetermined amount and means to increase the how of catalyst to said reactor when the heat difference decreases below a predetermined amount.

3. The control system of claim 1 wherein said means to control comprises means to reduce the tiow of material to be reacted to said reactor when the heat dilerence increases above a predetermined amount and means to increase the iiow of material to be reacted to said reactor when the heat difference decreases below a predetermined amount,

4. A polymerization system comprising a reactor, trst conduit means communicating with said reactor to supply material to be polymerized, means to measure the temperature of material passed through said iirst conduit means, means to measure the flow rate of material passed through said iirst conduit means, second conduit means communicating with said reactor to supply catalyst, third conduit means corrmunicating with said reactor to supply a solvent, means to measure the temperature of material passed through said third conduit means, means to measure the ilow rate of material passed through said third conduit means, a stirrer positioned in said reactor, means to rotate said stirrer, means to measure the energy employed to rotate said stirrer, fourth conduit means communicating with said reactor to remove reaction products, iifth conduit means in thermal contact with said reactor, sixth conduit means communicating with said fifth conduit 4means to supply coolant, seventh conduit means comaora-285 municating with said fifth conduit means to remove coolant, means to measure the temperature of coolant flowing through said sixth conduit means, means to measure the temperature of coolant removed through said seventh conduit means, means to measure the flow rate of coolant through said fifth conduit means, means to measure the temperature Within said reactor, means to measure the heat transferred through the walls of said reactor, means responsive to said means to measure to compute the difference between the heat removed from said reactor and the heat supplied to said reactor, and means responsive to said means to compute to control the operation of said reactor to tend to maintain the reaction at a uniform rate.

5. The system of claim 4 wherein said sixth and seventh conduit means and said means to measure the ilow and temperatures of said coolant comprise a coolant ash tank, means to pass liquid from said tank -to said fifth conduit means,` means to pass iluid from said iifth conduit means to said tank, means to measure the rate liquid is passed to said iifth conduit means, means to measure the temperature of the liquid passed to said fifth conduit means, a cooler, means to pass vapor from said tank through said cooler and to return condensed vapor to said tank, means to measure the How of uid from said cooler to said tank, means to measure the temperature of the fluid passed from said cooler to said tank, means to measure the temperature of liquid in said tank, and means to measure the temperature of vapor in said tank.

6. The system of claim 5 wherein said means to compute comprises means to multiply the How rate of the material to be polymerized by the speciiic heat of the material to be polymerized by the temperature difference between a reference temperature and the temperature of the material to be polymerized; means to multiply the flow rate of solvent by the specific heat of the solvent by the temperature difference `between said reference temperature and the temperature of the solvent; means to multiply the ow rate of coolant to said fifth conduit means by the specific heat of the coolant by the temperature differences of coolant removed from and supplied to said fifth conduit means; means to multiply the ow rate of coolant through said cooler by the specific heat of the coolant by the temperature difference upstream and downstream from said cooler; means to multiply the ow rate of coolant through said cooler -by the heat of vaporization of said coolant; means to multiply the iiow rate of material to be polymerized by the heat of solution of the material to be polymerized in the solvent; and means to add all of the resulting products and the energy to rotate said stirrer and the heat loss through the reactor walls.

7. In a polymerization system wherein the material to be polymerized and a catalyst are directed to a polymerization reactor, a coolant is circulated in thermal contact with said reactor, and polymerization products are withdrawn from said reactor; a control system comprising temperature sensing means to measure the ltemperatures of the material to be polymerized, the coolant passed to said reactor, the coolant removed from said reactor, and the polymerization products, flow measuring means to measure the flows of the material to be reacted, and the coolant removed from said reactor, means responsive to said temperature sensing means and said ow measuring means to compute the heat `generated within said reactor by the polymerization reaction, and means responsive to said means to compute to control the operation of the system to tend to maintain the reaction at a uniform rate.

8. In a polymerization system wherein the material to be polymerized and a catalyst are direc-ted to a polymerization reactor and the resulting products are removed from the reactor, a control system comprising means to measure the heat supplied to said reactor, means to measure the heat removed from said reactor, means to measure the difference between the heat supplied and the heat removed, and means responsive to said means to measure 2O the diterence to control the operation of the system to tend to produce polymer at a predetermined rate.

9. The method of controlling a polymerization process wherein the material to be polymerized and a catalyst are directed to a polymerization zone and the resulting prod ucts are removed from the zone which comprises measuring the heat added to the polymerization zone, measuring the heat removed from the polymerization zone, and regulating the operation of the process to tend to produce polymer at a uniform rate, as indicated by a constant difference between the heat removed and the heat added.

10. The method of claim 9 wherein the process is regulated by adjusting the rate at which the catalyst is di rected tothe polymerization zone.

11. The method of claim 9 wherein the process is regulated by adjusting the rate at which the material to be polymerized is directed to the polymerization zone.

12. A polymerization process comprising directing a l-oletin having no more than 8 carbon atoms per molecule and no branching nearer the double bond than the 4p0sition to a polymerization zone as a first stream; passing a catalyst comprising chromium oxide associated with at least one other oxide selected from the group consisting of silica, alumina, zirconia and thoria to said polymerization zone as a second stream; removing polymerization products from said polymerization zone, measuring the heat -added to said polymerization zone; measuring the heat removed from said polymerization zone; and regulating the ow of one of said streams to tend to produce polymer at a uniform rate, as indicated by a constant difference between the heat removed and the heat added.

13. A polymerization process comprising directing a l-olefin having no more than 8 carbon atoms per molecule and no branching nearer the double bond than the 4-position to a polymerization zone as a iii-st stream, passing a catalyst comprising chromium oxide associated with at least one other oxide selected from the group consisting of silica, alumina, zirconia -and thoria to said polymerization zone as a second stream; passing to said polymerization zone a liquid in which said 1olen is soluble; circulating a coolant in thermal contact with said polym` erization zone; removing polymerization products from said polymerization zone; measuring the heat added to said polymerization zone; measuring the heat removed from said polymerization zone; and regulating the flow of one of said streams to tend to produce polymer at a uniform rate, as indicated by a constant difference be tween the heat removed and the heat added.

14. A polymerization process comprising directing ethylene, cyclohexane and a catalyst comprising chromium oxide on a silica-alumina support to a reaction zone, agitating the mixture in said zone, cooling said zone, removing polymerization products from said zone, measuring the heat added to said zone from the introduction of ma terials and the agitation, measuring the heat removed from said zone from the withdrawal of material and the cooling, and regulating the flow of catalyst to said zone to tend to produce polymer at a uniform rate, as indicated by maintaining a constant difference between the heat removed and the heat added.

l5. ln a polymerization system wherein the material to be polymerized, a catalyst, and 4a diluent are directed to a polymerization reactor, the mixture is agitated in said reactor, a coolant is passed in thermal contact with said reactor, and the resulting product is removed from said reactor; a control system comprising, means to measure the temperature and flow rate of the material to be polymerized, means to measure the temperature and flow rate of the diluent, means to measure the temperature 5f the reactor, means to measure the heat supplied to the reactor by the agitation of the mixture in said reactor,

means to measure the heat lost from the reactor to the surrounding atmosphere, means to measure the liow ratel of coolant to said reactor and the temperatures of the:

coolant supplied to and removed from said reactor, and means responsive to said means to measure to compute `the difference between the heat removed from said reactor and the heat supplied to said reactor, thereby to provide an indication of the rate of polymerization.

16. A polymerization system comprising a reactor, first conduit means communicating with said reactor to supply material to be polymerized, means to measure the temperature of material passed through said first conduit means, means to measure the ilow rate of material passed through said first conduit means, second conduit means communicating with said reactor to supply catalyst, third conduit means communicating with said reactor to supply a solvent, means to measure the temperature of material passed through said third conduit means, means to measure the flow rate of material passed through said third conduit means, a stirrer positioned in said reactor, means to rotate said stirrer, means to measure the energy employed to -rotate said stirrer, 'fourth conduit means communicating with said reactor to remove reaction products, fifth conduit means in thermal contact with said reactor, sixth conduit means communicating with said fifth conduit means to supply coolant, seventh conduit means communicating with said fifth conduit means to remove coolant, means to measure the temperature of coolant ilowing through said sixth conduit means, means to measure the temperature of coolant removed through said seventh conduit means, means to measure the liow rate of coolant through said fifth conduit means, means to measure the temperature Within said reactor, means to `measure the heat transferred through the Walls of said reactor, and means responsive to said means to measure to compute the difference between the heat removed from said reactor and the heat supplied to said reactor, thereby to provide an indication of the rate of polymerization.

References Cited in the tile of this patent UNITED STATES PATENTS 2,402,137 Hanford et al June 18, 1946 2,440,882 Hachmuth May 2, 1948 2,497,323 Roedel Feb. 14, 1950 2,518,307 Groeke Aug. 8, 1950 2,570,056 Halbig Oct. 2, 1951 2,665,197 Rowland Jan. 5, 1954 2,683,141 Erchah July 6, 1954 2,684,326 Boyd July 2C, 1954 2,692,257 Zletz Oct. 19, 1954 2,825,721 Hogan et al Mar. 4, 1958 

14. A POLYMERIZATION PROCESS COMPRISING DIRECTING ETHYLENE, CYCOHEXANE AND A CATALYST COMPRISING CHROMIUM OXIDE ON A SILICIA-ALUMINA SUPPORT TO A REATION ZONE, AGITATING THE MIXTURE IN SAID ZONE, COOLING SAID ZONE, REMOVING POLYMERIZATION PRODUCTS FROM SAID ZNE, MEASURING THE HEAT ADDED TO SAID ZONE FROM THE INTRODUCTION OF MATERIALS AND THE AGITATION, MEASURING THE HEAT REMOVED FROM SAID ZONE FROM THE WITHDRAWAL OF MATERIAL AND THE COOLING, AND REGULATING THE FLOW OF CATALYST TO SAID ZONE TO TEND TO PRODUCE POLYMER AT A UNIFROM RATE, AS INDICATED BY MAINTAINING A CONSTANT DIFFERENCE BETWEEN THE HEAT REMOVED AND THE HEAT ADDED. 